Stereo photomicrography system

ABSTRACT

A stereo photomicrography system having a stereo microscope capable of viewing a specimen at various magnifications. Support structure for holding a stereo camera which can be optically aligned with the stereo microscope. A focusing microscope with a very shallow depth of field positionable over the stereo camera and adjustable to focus on a reticle that can be placed at the film plane of the stereo camera. A specimen holder which has height adjustment with respect to the stereo microscope and indicating mechanism associated therewith for producing readings of the height of the specimen. A photometer which can be utilized to measure the light intensity in the specimen image of the film plane. The use of this equipment wherein the various heights of the specimen and the light intensities taken at various magnifications of the microscope can be utilized in conjunction with the film speed to obtain stereo microphotographs at various magnifications providing sharp and clear stereo photos.

United States Patent 72] inventor Walter F. Lindsey Hampton, Va.

[21] Appl. No. 811,038

[22] Filed Mar. 27, 1969 [45] Patented Dec. 14, 1971 [73] Assignee TheUnited States of America as represented by the Administrator of theNational Aeronautics and Space Administration [54] STEREOPHOTOMICROGRAPHY SYSTEM 5 Claims, 2 Drawing Figs.

[52] U.S.Cl 95/18 [5 l 1 Int. Cl .1. G03b 35/08 [501 Field olSeorch95/l8;

[56] References Cited UNITED STATES PATENTS l,505,268 8/1924 Larsonass/22 nifications provi 2,614,454 10/1952 Steffen 2,639,653 5/1953Fischer ABSTRACT: A stereo photomicrography system having a stereomicroscope capable of viewing a specimen at various magnifications.Support structure for holding a stereo camera which can be opticallyaligned with the stereo microscope. A focusing microscope with a veryshallow depth of field positionable over the stereo camera andadjustable to focus on a reticle that can be placed at the film plane ofthe stereo camera. A specimen holder which has height adjustment withrespect to the stereo microscope and indicating mechanism associatedtherewith for producing readings of the height of the specimen. Aphotometer which can be utilized to measure the light intensity in thespecimen image of the film plane. The use of this equipment wherein thevarious heights of the specimen and the light intensities taken atvarious magnifications of the microscope can be utilized in conjunctionwith the film speed to obtain stereo microphotographs at various magdingsharp and clear stereo photos.

Patented Dec. 14,- 1971 3,626,828

2 Sheets-Sheet 1 IN I TOR. WALTER F. DSEY BY J 4M 5 C M64214 ATTORNEYSPatented Dec. 14, 1971 2 Sheets-Sheet 2 N Aim j mw q E INVENTOR. WALTERF. LINDSEY ATTORNEYS STEREO PHOTOMICROGRAPHY SYSTEM ORlGlN OF THEINVENTION The invention described herein was made by an employee of theUnited States Government and may be manufactured and used by or for theGovernment for governmental purposes without the payment of anyroyalties thereon or therefor.

This invention relates to a stereo photomicrograph system, and moreparticularly to such a system which will provide clearer and sharperstereo microphotographs.

Various procedures presently exist for obtaining stereo microphotos. Oneof the methods is by visually focusing the stereo microscope on thespecimen with the eyes focused at infinity so that the parallel rayswill emerge from the eyepieces. The stereo camera is then focused atinfinity with corrective prisms over the microscope eyepieces. With thecamera back off, the film plane is exposed and an average reading ofimage brightness is obtained at this point using a photoemissive tube.From this reading an approximate exposure is determined and the filmplaced in the camera and exposed. This procedure is a cut-and-tryprocedure which sometimes produced fairly good photographs and othertimes poor photographs.

Another technique of using the stereo microscope is that of using acamera which has the focus of its lenses fixed at different positions inconjunction with the microscope. Again focus and exposure is by trialand error resulting in a hit-andmiss arrangement.

The use of a ground glass screen or reticle located at the film planeprior to insertion of the film has also been utilized. With thisarrangement the image is formed on the reticle and departure from thefocus is fairly easily seen if the specimen contains rather contrastingareas. However, where the specimen image detail is very fine and lackingin contrast, the visible granularity or lines of the reticle itself makefocusing difficult.

The present invention overcomes the difficulties of the prior artmethods by providing an arrangement whereby sharp focusing of thespecimen is obtained with the use of a focusing microscope and specimenheight adjusting device prior to exposure of the film. In addition, thelight intensity for a particular focus is accurately ascertained, thisdata being utilized in conjunction with specimen height and the filmspeed to provide an exposure setting which results in sharp and clearstereo microphotos. Q

It is therefore an object of the invention to provide a a stereophotomicrography system which will produce sharply defined images withan optimum depth of field.

Yet another object of the invention is to provide a stereophotomicrography system which utilizes a focusing microscope having asmall depth of field.

Another object of the invention is to provide a stereo micrographysystem having a specimen support with height adjustment, and associatedmechanism to measure the position of the specimen.

A further object of the invention is to provide a stereo micrographysystem which uses a photoconductive cell having a very small diameterfor examining the image brightness.

Still another object of the invention is to provide a stereo micrographysystem that will produce a high-quality photograph, quickly andreliably.

An added object of the invention is to provide a method for producingstereo microphotographs.

These and other objects and advantages of the invention will become moreapparent upon reading the specification in conjunction with theaccompanying drawings.

In the drawings:

F IG. 1 is a front elevational view of the stereo photomicrographysystem; and

F IG. 2 is a side elevational view of the stereo photomicrographysystem.

Referring now more specifically to the details of the invention, FIGS. 1and 2 show the stereo photomicrography system designated generally bythe reference numeral 10.

sides are joined together by cross bracing and positioned at the top isa platform 12. The platform 12 is pivotally mounted on screws extendingthrough the sides of the support. The screws are provided with wing nutsfor tightening the platform between the sides of the stands andmaintaining it in a desired position.

A stereo camera 15 is supported by the platform 12 in a conventionalmanner. Most any type of commercially available stereo camera may beutilized; however, for purposes of this invention, the Stereo Realistcamera was used. This camera has a back which is movable, the opening inthe back of the camera being designated by reference numeral 16 in thedrawings. The camera hasa pair of lenses 17 which are associated withcorrective prisms 18, the prisms being utilized to optically align thestereo camera with the eyepieces of the stereo microscope to bedescribed more fully hereinafter.

The reference numeral 20 designates a reticle or ground glass structurewhich is utilized in focusing the camera on the specimen. The reticle 20is positioned at the film plane of the stereo camera to assist focusing,and after it has served its purpose removed and the camera loaded withfilm.

Positioned adjacent camera stand I! is a platform 25 which is utilizedto hold a focusing microscope 28. Included in the platform assembly 25is an X, Y, Z positioning mechanism which consists of a series of racksand pinions with associated turning knobs for movement in the Variousplanes.This mechanism is of conventional design and is similar inconstruction to a schlieren knife edge X, Y, Z positioning structure.Connected to the positioner is adjustable linkage 27 which is utilizedto hold the focusing microscope 28 in position over the stereo camera25.

The focusing microscope 28 is again structure which is availablecommercially, and for purposes of the invention should be of moderatepower, for example about 50 X, have a fairly large field coverage, but avery small depth of field (a few thousandths of an inch).

A pedestal 35 with positioning apparatus 36 supports the stereomicroscope 37. The eyepiece 38 of the microscope are aligned with thecorrective prisms 18. Various types of stereo microscopes might beutilized; however, the particular instrument utilized in the setup shownin FIGS. 1 and 2 was a Cycloptic Stereoscoptic Microscope made by theAmerican Optical Company. This particular microscope has a turret withpositive stops which allows various powers of magnification to beutilized. The magnification can also be varied by changing one or bothof the eyepieces and/or the objective lenses. One of the eyepieces has afixed focus whereas the other is adjustable.

Lights 45 for illuminating the specimen are in the nature of a goosenecklamp which has a base and flexible neck which extend therefrom and canbe positioned relative to the specimen.

A specimen holder 48 is located adjacent to the stereo microscope 37.The specimen holder 48 has a generally rectangular-shaped frame with amicrometer adjusting screw 50 threaded through the top of frame. Aturning knob 51 is connected to the adjusting screw 50. Connected to theadjusting screw 50 is a specimen holding plate 49 which is raised andlowered relative to the microscope upon turning the adjusting screw.Specimen 53 is shown lying on the plate 49 in position under the stereomicroscope. A portion of the plate extends beyond the holder frame andis located to enable contact by a measuring instrument now to bedescribed.

The measuring instrument is designated generally by the referencenumeral 57 and is of the dial indicator type capable of measuringposition to 0.001 inch such as sold by the Star rett instrumentCorporation. As with the usual dial indicator apparatus, a stand 59 isprovided with an arm 58 which holds and may be utilized to position theindicator at the proper position. This is best illustrated in FIG. 1 ofthe drawings.

4 enable examination of various parts of the image for improved exposuredetermination and control in a manner to be described more fullyhereinafter.

METHOD AND OPERATION Having discussed the apparatus above, the procedurefor utilizing the apparatus to obtain clear and sharp microphotos willnow be explained.

The specimen holder 48 is set so that measureable up-anddown motion isobtainable. The holder is positioned so that the specimen 53 issupported on the holder plate 49 under the stereo microscope objectivelens 39. The stereo microscope is raised or lowered to bring thespecimen into visual focus through the fixed eyepiece which is one ofthe eyepieces 38. The movable eyepiece, which is the other eyepiece, isadjusted to the same height as the fixed eyepiece so that it has thesame focus. The spacing of the microscope eyepiece 38 are then adjustedto the same spacing as the lens 17 on the stereo camera which ispositioned above the eyepieces of the stereo microscope. Proper heightand alignment of the stereo camera can be obtained by adjusting theheight of the stand 11 and tilting of the platform 12. On completion ofthe microscope and camera alignment the corrective prisms 18 are placedover the stereo microscope eyepieces and beneath the lenses of thestereo camera. The stereo camera is located over the eyepieces of thestereo microscope so that the optical axis of the microscope ascorrected by the prisms coincides with the optical axis of the camera.Throughout the remainder of the procedure, the stereo camera 15corrective prisms l8, and the stereo microscope 37 remain fixed withrespect to each other, unless for some reason the adjustable eyepiecegets out of focus with the fixed eyepiece.

The back of the camera 15 is removed and a ground glass or lined reticle20 is positioned in the same place that the camera film would occupyassuming the camera was loaded with film. With the light 45 turned off,the focusing microscope 28 is positioned over the reticle 20 at thefixed eyepiece position of the stereo microscope. Proper location of thefocusing microscope 28 can be obtained by operation of the X, Y, Zpositioner 26. The focusing microscope 28 is carefully focused on thelined reticle 20. Upon completion of focusing, the reticle is removedand the lights 45 beamed onto the specimen 53. The specimen 53 is raisedor lowered by the specimen holder adjusting screw 50 until it is sharplyin focus as viewed through the focusing microscope 28. A lined reticlecan now be placed at the film plane above the adjustable eyepiece andsharp focusing obtained by adjusting the eyepiece and not the specimenheight. This adjustment of the eyepiece may permit a slight increase inapparent depth of field; however, if the adjustable eyepiece wasoriginally focused to coincide with the fixed eyepiece, this operationmay not be necessary. Thus assuming that both eyepieces are focused, thespecimen height is recorded by taking a reading from the dial indicator57. As is apparent in FIG. 1, the arm 58 of the dial gage 57 contactsthe extension of plate 50 providing a height reading for the specimen.

The photoconductive cell 56 is then placed in the available image planeof the stereo camera. The reading on the photometer 65 is recordedindicating the brightness of the image viewed. The magnification atwhich the specimen is being viewed through the stereo microscope is alsorecorded.

With this information available, it is possible to load the camera withfilm and by utilizing the data collected, expose the film and obtain aclear sharp microphoto. However, since it is usually desirable to takepictures at various magnifications, data is normally secured for variousmagnifications prior to loading the camera with film and taking thepictures.

ln order to obtain all the data prior to taking pictures, themagnification of the stereo microscope is changed by rotating the lensturret or by other techniques as previously mentioned. The specimenholder 48 is again adjusted until the specimen is sharply defined in thefocusing microscope 28. The height of the specimen is again recordedfrom the dial gage 57, and the photometer reading recorded. Readings ofthe height of specimen and brightness indicated by the photometer arethen recorded for each variation and magnification of the stereomicroscope. These readings are taken, however, without having moved thefocusing microscope 28, camera 15 or stereo microscope 37.

The camera is loaded and the film exposed in accordance with the datapreviously gathered. For each magnification the specimen holder is setat its previously determined height for that magnification. Exposure isthen made by utilizing the data as gathered for this setting. Since thephotometer 65 is calibrated to be converted into image brightness (b) incandles per square foot, the exposure of the film in seconds can becalculated from the formula T=l/1rbs where s is the ASA speed rating ofthe film.

ln operating the apparatus, it was found that often when the objectivelenses were changed or the eyepieces of the stereo microscope changedgreatly in magnification, the working distance of the microscope shiftedto such an extent that an adjustable height range of the specimen holder48 and the dial indicator 57 was exceeded. When this occurred, it wasnecessary to repeat the entire procedure described above. It should berecognized, however, that by changing the objective lenses and/oreyepieces, as utilized in conjunction with the turret lenses, that alarge range of magnifications at various increments is obtainable.

From the above description, it should be clear that the guesswork hasbeen eliminated regarding proper focusing of the specimen on the filmplane enabling sharp and clear photographs to be taken. Furthermore, byutilizing the method suggested, pictures covering a range ofmagnification can be obtained on a single roll of exposed film. Use of aphotoconductive cell in conjunction with the photometer wherein thephotosensitive area of the cell is quite small allows various parts ofthe image to be examined for improved exposure determination or control.The use of many commercially available items in the environment of thisinvention provides a combined apparatus which is highly reliable,accurate and provides maintenance-free operation.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

l. The method of obtaining stereo microphotos comprising:

fixing a stereo camera, corrective prisms, and a stereo microscoperelative to each other;

placing a specimen under the stereo microscope;

focusing the microscope eyepieces on the specimen;

aligning the optical axis of the camera with the microscope using thecorrective prisms;

placing a reticule at the film plane in the camera;

focusing a focusing microscope on the reticule;

removing the reticule;

lighting the specimen;

moving the specimen up or down to bring it into sharp focus with thefocusing microscope;

recording the height of the specimen;

obtaining a light reading from a photometer;

recording the stereo microscope magnification;

loading the camera with film; and

exposing the film at the specimen height, light reading andmagnification previously recorded.

2. The method of obtaining stereo microphotos as in claim 1 .wherein theposition of the specimen and the light readings are obtained for variousstereo microscope magnifications prior to exposing the film; said filmbeing exposed at the various magnifications with corresponding specimenheights and light readings.

3. The method of obtaining stereo microphotos as in claim 2 includingthe step of maintaining the focusing microscope, stereo camera, andstereo microscope in fixed relative position while readings are obtainedat the various magnifications.

1. The method of obtaining stereo microphotos comprising: fixing astereo camera, corrective prisms, and a stereo microscope relative toeach other; placing a specimen under the stereo microscope; focusing themicroscope eyepieces on the specimen; aligning the optical axis of thecamera with the microscope using the corrective prisms; placing areticule at the film plane in the camera; focusing a focusing microscopeon the reticule; removing the reticule; lighting the specimen; movingthe specimen up or down to bring it into sharp focus with the focusingmicroscope; recording the height of the specimen; obtaining a lightreading from a photometer; recording the stereo microscopemagnification; loading the camera with film; and exposing the film atthe specimen height, light reading and magnification previouslyrecorded.
 2. The method of obtaining stereo microphotos as in claim 1wherein the position of the specimen and the light readings are obtainedfor various stereo microscope magnifications prior to exposing the film;said film being exposed at the various magnifications with correspondingspecimen heights and light readings.
 3. The method of obtaining stereomicrophotos as in claim 2 including the step of maintaining the focusingmicroscope, stereo camera, and stereo microscope in fixed relativeposition while readings are obtained at the various magnifications. 4.The method of obtaining stereo microphotos as in claim 1 wherein thereticle is again placed in the camera film planes after adjustment ofspecimen height by sharp focusing with the focusing microscope andadditional sharp focusing of the specimen is obtained by focusing thestereo microscope adjustable eyepiece.
 5. The method of obtaining stereomicrophotos as in claim 1 wherein a selected area of interest of theimage is examined by the photometer.